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I've replaced the alternator and signal generator on my 1998 Suzuki Intruder VL 1500 and since it back fires like crazy and most of the time will not start or run without full choke. I'm thinking this is related to ignition timing after seeing posts on various forums about others with the same issue however while reading the Hanes manual for the bike, it states the following:

On carbureted models, the ignition system consists of a signal generator, igniter with an 8-bit microprocessor (IC), two ignition coils and two park plugs. During operation, the IC in the igniter receives input from the signal generator, throttle position sensor, and MAP sensor to determine the ignition timing for the operating conditions.

The IC sends a signal to the ignition coil, the primary winding turns off and on, and a high voltage is induced in the secondary winding, which fires the spark plug.

It says nothing there about a "distributor". Does this bike have a distributor and how can I adjust ignition timing?

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The wording you have posted there suggests there is not a distributor. Instead, the IC calculates timings and triggers the ignition coil.

If the bike needs full choke even when warm, it's worth looking at your MAP sensor and throttle position sensor to see if they are faulty. The various motorcycle forum posts on this also suggest looking at CKP, CMP, ignition module, electrical faults, exhaust valves etc... so there are a lot of things that could have an impact.

  • What would have caused this change after a simple alternator / stator coil change? @Rory Alsop – 0perator Apr 3 at 15:11
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As stated in the service manual, this bike does not have a distributor and instead uses the signal generator (inside the clutch / alternator cover) to send data along with various other sensors to the ignition system to calculate timing on it's own.

RESOLUTION:

The reason for the backfiring / hard running was that timing was off due to the polarity being reversed on the new signal generator. The alternators (non OEM) for these bikes seem to be pretty generic and certain models / brands will require reverse polarity from what the alternator is wired for stock. To correct this, simply reverse the wires OUTSIDE of the clutch / alternator housing - other wise you will strip the protective coating off from inside the housing where the wire will be exposed to hot oil and degrade over time.

From the service manual, I'll leave you with the below information in hopes that this helps someone else not spend the countless hours I did trying to track this crazy problem down.

On carbureted models, the ignition system consists of a signal generator, igniter with an 8-bit microprocessor (IC), two ignition coils and two park plugs. During operation, the IC in the igniter receives input from the signal generator, throttle position sensor, and MAP sensor to determine the ignition timing for the operating conditions.

The IC sends a signal to the ignition coil, the primary winding turns off and on, and a high voltage is induced in the secondary winding, which fires the spark plug.

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